This project involves utilization of single neuron recording and operant conditioning techniques in behaving monkeys to study brain mechanisms underlying voluntary movement. Monkeys are trained to make precise movements of a handle whose movement controls a visual display, and stimuli are delivered via the handle by means of an electronically controlled torque motor in order to determine how sensory feedback is processed. Using these methods we have obtained the first data on activity of identified descending output neurons from somatosensory cortex during voluntary movement in the monkey and have found that these neurons have three properties in common with the descending output neurons of motor cortex: (i) they exhibit discharge prior to movement onset, (ii) their discharge frequency varies as function of strength of muscular contraction and (iii) they show reflex responses to afferent stimuli occuring during movement. These findings suggest that in addition to its widely recognized role in perception, somatosensory cortex also has a role in control of movement.